In recent years, in digital equipment such as a cellular phone or digital television, demand for various digital processing such as sound processing, audio processing, video processing, and code processing has grown. To implement the digital processing, an information processor such as a microprocessor is used normally. To respond to an increase in demand for applications, a circuit scale, an operation frequency, and the number of mounted processors have also increased so that power consumption has kept on increasing.
To reduce power consumption, control operations have been performed conventionally and generally, such as clock gating control using hardware, a control operation which suspends an operationally unneeded block using software, and a control operation (Japanese Laid-Open Patent Publication No. HEI 8-152945) which changes a frequency and a voltage status on a per program basis using software or hardware. It is assumed herein that the expression “a per program basis” in the specification implies a per process basis, a per thread basis, and a per task basis.
In recent years, there has also been performed a control operation which changes a frequency and a voltage status depending on an average load state over a long cycle period in the status of execution of a processor (Japanese Laid-Open Patent Publication No. HEI 8-6681).    Patent Document 1: Japanese Laid-Open Patent Publication No. HEI 8-152945    Patent Document 2: Japanese Laid-Open Patent Publication No. HEI 8-6681